Reactions of 3,3-dimethylbut-1-ene with deuterium or deuterium oxide on oxide catalysts

Abstract

The reactions of 3,3-dimethylbut-1-ene (I) over a copper X zeolite, magnesium oxide and γ-alumina have been studied in the presence of either deuterium or deuterium oxide. Products obtained by exchange and/or isomerization have been analysed using a combined gas chromatograph-mass spectrometer. Over CuX with D₂O, I underwent isomerization at 417 K to give 2,3-dimethylbut-1-ene (II) and 2,3-dimethylbut-2-ene (III), but did not itself exhibit direct exchange. Both II and III formed initially showed similar but extensive incorporation of deuterium. On magnesium oxide with D₂ at 493 K, I exchanged, the vinyl hydrogens being replaced faster than those in the methyl groups. No isomerization was detected. Over γ-alumina at 328 K and with D₂ present, I rapidly isomerized to give a mixture of II and III, but little deuterium incorporation accompanied this reaction and only a very limited exchange of I occurred.